[fuchsia] Stop using deprecated way to Allocate/DeallocateBlock

After this CL and another goldfish-vulkan ICD roll, we
can then clean up the device interface in fuchsia tree:

https://fuchsia-review.googlesource.com/c/fuchsia/+/346311

Change-Id: I45d1d95f465798ae17c3eec10192f5b3df066377
2 files changed